Corneal Dystrophy in Dogs

My Cavalier King Charles spaniel developed some haziness in his eyes. He was 2 years old at the time, and had not had any injury I was aware of. It didn’t seem to affect his vision, but it was really noticeable. My regular veterinarian sent me to a veterinary ophthalmologist who diagnosed a condition called “corneal dystrophy”.  She said there were different types, and I’m still a bit confused about this condition.

Corneal dystrophy is a term used to describe several conditions that occur in dogs and cause the corneas to become opaque. There are three major categories of corneal dystrophy: epithelial, stromal, and endothelial. Each is named by the anatomic location of the abnormal tissue and opacity. All corneal dystrophies are primary, inherited conditions not associated with any other eye disease or systemic (body-wide) medical problem. Corneal dystrophy is very rare in cats.

What are the three types of corneal dystrophies?  How do they differ from one another?

The three types of corneal dystrophy are named by their anatomic location in the cornea, and consequently the clinical signs of each differ.

1.      Epithelial corneal dystrophy
This opacity occurs in the superficial layers of the cornea. It is described in Shetland sheepdogs with onset occurring between  6 months and 6 years of age. Dogs with epithelial corneal dystrophy may have no clinical signs other than corneal opacity; however, they may have corneal pain causing sensitivity to light, and squinting. The surface of the eye may develop patches of white or gray—these are the opaque lesions—and some of the lesions may reflect erosions in the corneal surface. The erosions are what lead to eye pain.

2. Stromal corneal dystrophy
The stroma is the middle layer of the cornea, and stromal corneal dystrophy is associated with the deposit of fat droplets into this layer of the cornea. Multiple breeds are affected including (but not limited to):

Airedales
Cocker spaniels
Bearded collies
Cavalier King Charles spaniels
Samoyeds
Weimeraners

These dogs tend to be young when diagnosed, and most dogs have no associated inflammation or pain. The opacity tends to occur in one of several patterns, most commonly as a gray, white, or silver opacity at or near the center of the cornea. Alternately, the opacity may appear as a ring around the outer border of the cornea, or the entire cornea may become diffusely opaque. Vision may be affected when the opacity is diffuse.

3. Endothelial corneal dystrophy
Endothelial corneal dystrophy affects the deepest layer of the cornea, and these dogs tend to be middle aged or older when their signs appear. Boston terriers, Chihuahuas, and Dachshunds are the primary breeds affected. In its early stages, there may be no easily observable signs. As it progresses, fluid accumulation (edema) starts at the lateral edge of the cornea and spreads across the rest of the cornea over time. These dogs may develop painful corneal ulcers, and may lose their vision with advanced disease.

Is there any treatment for corneal dystrophy?

Advanced epithelial or endothelial corneal dystrophy may result in corneal ulceration that requires treatment. That treatment may require referral to a veterinary ophthalmologist. Otherwise, no treatment is described or required for the various corneal dystrophies. It is worth noting that most dogs with corneal dystrophy never experience compromised vision.